As a piece of equipment that performs an essential function with only sunlight for fuel, the solar cooker has caught the imagination of many since the late 18th century. Over the past few decades, several hundred thousands of these gadgets have been put to use; there were 617,000 in India in 2007. They serve as recreational cooking gear in the backyard of affluent American homes. In resource-poor Indian villages, Darfur refugee camps, and poor communities setting up food ventures, they act as a vital facility. Although not suitable for a fast-paced, instant-cooking lifestyle, design variants of the solar cooker hold promise. Perhaps the best-known installations of scale in India are those at Tirupati, Shirdi, and Mount Abu, where several thousand meals are cooked everyday. With policy support, solar cookers can play a greater role in easing the pain of rising cooking gas prices for the middle class. Solar box cookers for the home raise the temperature to about 140 degrees Celsius by trapping the sun’s heat in a black enclosure. Other designs concentrate the heat using a reflecting parabolic dish, cooking the food directly or by generating steam in pipelines; some have the facility to track the sun’s movement. The slow-cooking method suits some foods well, retaining natural moisture and vitamins. But it is unsuitable where quick results or frying are important.
Many residents of the hotter cities would be tempted to give solar box cookers a try, as a supplement to liquefied petroleum gas. Without subsidy, a cooker costs the equivalent of four LPG cylinders. The Tamil Nadu Energy Development Agency estimates LPG savings of 20 to 40 per cent for a normal pattern of use based on the cooker model. Yet, it must not be forgotten that the existing performance levels have been achieved with only basic research on design and materials. Official policy could do much more to encourage innovation. Better heat retention in the cookers using thermal fluids is being attempted. Good results have also been obtained from newer insulation materials in U.S. models. A beginning could be made by making the existing cookers cheaper and more widely available. The solar thermal industry is pinning its hopes on institutions, but it may find residential communities primed for adoption too. Steam and thermal pipeline technologies hold great potential for large real estate projects. On the question of subsidy, the Ministry of New and Renewable Energy will no doubt see the anomaly of depriving solar box cookers of the benefit, while LPG consumers continue to enjoy it.